During the past year, research has been pursued concerning (1) Etiological mechanisms underlying individual differences in alcohol consumption in rhesus monkeys, with an emphasis on paternal genetic contributions; (2) The effect of early experience on the development of social competence and the nervous system; (3) The relationship between serotonin (5HT) and social behavior in laboratory and feral-living nonhuman primates. The role serotonin plays in social behavior and the acquisition on social competence was investigated in carefully controlled laboratory settings. To assess the generalizability of our laboratory findings, and to obtain a subject pool of inappropriately aggressive individuals with sufficient numbers to perform parametric analyses, we continued to investigate ferally-living adolescent male monkeys drawn from a subject pool of 4500 rhesus monkeys living on an island off the coast of South Carolina; (4) Developmental patterns and predictors of rhesus monkeys selectively bred for extremes in CSF 5-HIAA. A major part of the past year has involved the development of a selective breeding program to breed for extremes in CSF 5-HIAA concentration. Both the parents and the infants have been carefully assessed to investigate parental genetic contributions to excessive aggression and alcohol consumption; (5) Genetic differences in the 5HT system using molecular genetics techniques, including amplification of the 5HT 1A receptor gene in feral and laboratory lineages of rhesus macaques and in different species of monkeys that exhibit increased or diminished CSF 5-HIAA, development of fibroblast cell lines to acquire increased DNA, and the development of techniques to type for tryptophan hydroxylase; (6) Pharmacological treatment of excessive alcohol consumption using the 5HT 1A agonist ipsapirone. (7) Initiation of PET scan paradigm to assess neurobiological differences in aggression in intact nonhuman primates.